1. Field of the Invention
The present invention relates to an image-capturing device such as an electronic camera that employs a solid image-capturing element such as a CCD and, in particular, it relates to an image-capturing device achieving a vibration-proofing function for eliminating adverse effects of an unsteady hand movement and the like.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. H 7-248522 discloses an electronic camera achieving a so-called vibration-proofing function that prevents the quality of an image from becoming degraded due to the adverse effects of an unsteady hand movement by implementing shift-drive of a photographic lens element along the direction perpendicular to the optical axis of the photographic lens in order to cancel out the effect of the hand movement.
As we see increasing numbers of notebook-type personal computers and mobile telephones mounted with compact on-board cameras marketed in recent years, the demand for smaller, less expensive electronic cameras (electronic still cameras and video cameras) has intensified. Keeping pace with this demand, much effort is being put into making image-capturing elements smaller and to achieve further miniaturization of the photographic image plane. As a result, the focal length of a photographic lens for covering a given photographic field angle has become smaller, and a normal photographing operation can be performed through a so-called “pan focus” operation, which does not require the photographic lens to be moved along the direction in which the optical axis extends for focusing and allows it to be set at a specific fixed position.
The extent to which image quality degrades due to an unsteady hand movement or the like, which changes in proportion to the relationship between the photographic field angle and the angle of the hand movement, is not affected by the size of the photographic image plane if a photographing operation is performed at a fixed field angle. In other words, while the focusing function becomes unnecessary or at least less important in a normal photographing operation as the image-capturing element or the photographic image plane becomes smaller, vibration-proofing is still as necessary and effective a function as in a conventional camera with a larger image-capturing element and a larger photographic image plane. It is to be noted that while the need to achieve focus at the photographic lens is less rigorous in a camera having a smaller image-capturing element, defocusing occurs readily if the positional relationship between the image-capturing element and the photographic lens becomes offset along the direction in which the optical axis extends even by a slight degree and thus, more exacting requirements are imposed with regard to the positional accuracy along the optical axis.
In addition, the vibration-proofing mechanism itself must become smaller and lighter in conjunction with a miniaturized image-capturing element in order to achieve a more compact and lightweight photographing device.
A considerable difficulty exists in attempting to achieve the requirements imposed on electronic cameras in recent years, i.e., reduced size and weight, through the structure of the electronic camera with the conventional vibration-proofing function explained in reference to the related art which requires numerous components including the vibration-proofing drive mechanism (for shifting the lens, for instance) and a vibration detection sensor and thus does not facilitate the process of assembly either. Furthermore, since a complex structure is assumed in the electronic camera, it is difficult to maintain a satisfactory degree of accuracy with regard to the relative positions of the photographic lens and the image-capturing element along the optical axis.